Evaluating forecasts of the evolution of the cloudy boundary layer using diurnal composites of radar and lidar observations
Barrett, A. I., Hogan, R. J. and O'Connor, E. J. (2009) Evaluating forecasts of the evolution of the cloudy boundary layer using diurnal composites of radar and lidar observations. Geophysical Research Letters, 36 (17). L17811. ISSN 0094-8276
To link to this item DOI: 10.1029/2009GL038919
Observations of boundary-layer cloud have been made using radar and lidar at Chilbolton, Hampshire, UK. These have been compared with output from 7 different global and regional models. Fifty-five cloudy days have been composited to reveal the mean diurnal variation of cloud top and base heights, cloud thickness and liquid water path of the clouds. To enable like-for-like comparison between model and observations, the observations have been averaged on to the grid of each model. The composites show a distinct diurnal cycle in observed cloud; the cloud height exhibits a sinusoidal variation throughout the day with a maximum at around 1600 and a minimum at around 0700 UTC. This diurnal cycle is captured by six of the seven models analysed, although the models generally under-predict both cloud top and cloud base heights throughout the day. The two worst performing models in terms of cloud boundaries also have biases of around a factor of two in liquid water path; these were the only two models that did not include an explicit formulation for cloud-top entrainment.